turre



G. J. TURRE 2,882,498

GALVANOMETER April 14, 1959 3 Sheets-Sheet 1 Filed Sept. 20, 1956 INVENTOR. GEORGE J. TU RRE r ta Q4. Q ZL A'rromusvs G. J. TURRE GALVANOMETER I Api-i'l 14, 1959 5 Sheets-Sheet 2 Filed Sept. 20, 1956 ATTomvEYs United States Patent GALVANOMETER George J. Turre, Lakewood, Colo., assignor to Hamilton Watch Company, Denver, Colo., a corporation of Pennsylvania This invention relates to galvanometers for use in oscillographs, and the like, and particularly to an improved galvanometer of the type atfording the mounting of a large number of galvanometers in a small space.

Some types of instruments which utilize galvanometers are required to have a large number of galvanometers in a small space. For example, in portable oscillographs it may be desirable to record a large number of electrical characteristics on a single record; because of space and weight considerations a very compact design of the galvanometers and their mountings is required. Furthermore, especially in oscillographs for field use, it is desirable that the galvanometers "be easily adjusted and replaced and that the structural features of the assembly be simplified as much as practicable. Accordingly it is an object of the present invention to provide a galvanometer including an improved arrangement for assembling the galvanometer and its mounting.

It is another object of this invention to provide a galvanometer including an improved housing and mounting arrangement for the parts thereof. Briefly, in carrying out the objects of this invention in one embodiment thereof, the moving element or coil of a galvanometer is suspended in an elongated frame of generally cylindrical form with a central axial passage for the suspension and side passages or openings for the pole tips and for access to the galvanometer mirror. Detachable magnetic pole'pieces are placed in openings adjacent the coil of the galvanometer and are held in place by a thin walled housing of non-magnetic material which is slipped over the frame and encloses the suspension. The assembled element is mounted in a socket member or cradle provided with a spring pressed detent to hold it in place against axial displacement, but from which the element may easily be removed by a lifter provided on the magnet assembly of the galvanometer. The dimensions of the element are small and multiple elements may be mounted in a small space. Electrical connections are made by friction contacts and are opened upon lifting the element from its latched position.

The features of 'novelty which characterize the invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

'Fig. l is a front elevation view of a multiple galvanometer unit embodying the invention;

Fig. 2 is an end elevation view of the unit of Fig. 1 with the end cover removed;

Fig. 3 is an enlarged view similar to Fig. 2 with portions shown in sect-ion along the line 3-3 of Fig. 1;

Fig. 4 is an enlarged top plan view of a portion of the unit;

. Fig. 5 is an enlarged front elevation view partly in section of one of the galvanometers of Fig. 1;

Fig. 6 is a sectional side elevation view of the galvanometer of Fig. 5;

Fig. 7 is an enlarged view partly in section of the lower end of the galvanometer of Figs. 5 and 6;

Fig. 8 is an enlarged sectional view along the line 88 of Fig. 6;

Fig. 9 is a front elevation view partly in section showing the moving element of the galvanometer; and

Fig. 10 is a partially exploded view of the galvanometer of Fig. 5 illustrating the method of assembly.

Referring now to the drawings, the galvanometer assembly illustrated in Figs. 1 and 2 is of the multiple element type and comprises a magnetic base structure 10 in which twelve thin elongated galvanometer elements 11 may be mounted; in the drawing the extreme right-hand element has been removed and the third and fourth elements from the right are shown in their raised position prior to being locked in place. The magnetic structure 10 is enclosed at its two ends by plates 12 and 13 and in Fig. 2 the plate 13 has been removed to show the interior arrangement of the parts. The magnetic structure comprises a base portion 14 having stepped ends on which are mounted permanent magnets 15 and 16. The galvanometer elements 11-are mounted in individual sockets or cradles 17 of brass or other suitable nonmagnetic material; these cradles have magnetic pole tips 18 and 19 with cylindrical outer surfaces conforming to and engaging pole pieces 20 and 21 on the magnets 15 and 16, respectively. The cylindrical face construction of the pole tips 18 and 19 is provided so that the cradle 17 may be rocked forward or backward in the assembly to adjust the vertical position of the light beam reflected from the galvanometer mirror through a window in a boss 22. Each of the galvanometers 11 may be removed by rotating a release finger 23 clock: wise as viewed in Fig. 2 to press -a toe.24 against a lug 25 on the galvanometer housing, thereby lifting the galvanometer to a position as indicated by the two raised galvanometer elements in Fig. 1. The fingers 23 are made of non-magnetic material and are pivotally mounted on a non-magnetic bar 26 secured to the top of the structure across the pole pieces 21. The electrical leads or connections for the galvanometers are brought out to a plug board 27 secured to the bottom of a structure 10 on spacers or legs 28.

The manner in which each of the galvanometers 11 is mounted in its corresponding cradle 17 is shown in the enlarged sectional view, Fig. 3. The lower end' of the housing of the galvanometer 11 is provided with an annular groove 30, and when the galvanometer is in its lower position as shown a movable detent 31 biased inwardly by a spring 32 is engaged in the groove 30 and latches the galvanometer in position resting against an internal bushing or sleeve 33 in the lower end of the cradle 17. Areduced extension or connection post 34 on the galvanometer fits within the internal bore of the sleeve 33 and contacts 35 and 36 on the extension engage insulated conductors 37 and 38, respectively, which are the electrical connections to the galvanometer moving element. The release fingers 23 are pivotally mounted on a shaft 40. The shaft 40 is secured to the bar 26 in open-topped bearings in lugs 41, as shown in Fig. 4,

and is locked in position by several pins 42, one of which is shown in Fig. 4; these pins are secured by a pressed fit in openings in the block 26 and bear against the top of the shaft 40. When the finger 23 is rocked clockwise to the dotted-line position in Fig. 3, the toe 24 lifts the galvanometer 11 to the dotted-line position as indicated. When the finger is released it springs back from its dotted-line position to its full line position as shown; this action is caused ,by magnetic attraction between the magnet poles and a magnetic screw 23a threaded into the bottom of the toe 24 which biases the finger to its full line position. In order to adjust the 'galvanometer for vertical deflection, individual screws 43 are mounted in the blocks 26 and each has a ball and socket connection 44 engaging the top of the respective pole pieces '19 so that the pole pieces may be rocked and the galvanometer housings adjusted by turning the screws 43. Adjustment of the horizontal direction of the galvanometer beam is effected by turning the galvanometer housing about its longitudinal axis in the cradle 17.

The details of construction of the galvanometer 11 are shown in Figs. through inclusive. The galvanometer 11 comprises an outer housing 46. of non-magnetic material which is in the form of an elongated cylinder having its upper end slotted as indicated at 47 and formed to provide an internal shoulder 48. The thickness of the wallet the housing 46 is made as thin as practicable consistent with the strength desired so that a minimum non-magnetic path or air gap is interposed between the pole pieces of the galvanometer and the pole structure of the magnetic circuit. The diameter of the bore is reduced as indicated at 49 at the upper end of the housing and this provides the shoulders 48 previously mentioned. The galvanometer suspension is mounted in a non-magnetic frame 50 of generally cylindrical form which fits within the bore of the housing 46 and engages the annularshoulder 48. The tension on the moving element of the galvanometer may be adjusted by turning a screw 52 before assembling the frame 50 in the housing 46. The frame 50 has a central here or passage '53 extending therethrough and which the moving element of the galvanometer, indicated generally at '54, is secured on cross pins 55 and 56, the cross pin 56 being anchored to the housing 46 and the pin 55 mounted'in a slide block'57 engaging the adjusting screw 52 as indicated in Fig. 9. The frame 50 is provided with access. windows 59 and 60 opposite the pins 55 and 56 and with elongated access openings 61 and 62, above and below the coil of the moving element indicated at 63 in Figs. 8 and 9. In addition the frame 50 is provided with oppositely disposed rectangular openings 64 and 65 on either side of the coil position in which are mounted pole pieces 66 and 67 having arcuate outer surfaces conforming to the inner walls of the housing 46 and having inner faces 68 and 69 lying parallel to on'eanother on either side of the coil 63. The openings 64 and 65 are cut to provide surfaces parallel to one another .and which provide seats for the sides of the pole pieces 66 and 67. The galvanometer mirror as indicated at 71 lies opposite the window 22 and is visible through the opening 61. The post 34 on which the contacts '35 and 36 are mounted extends beyond the lower end of the casing 46 and the frame 50 is secured in position within the housing by a nut 72 fitted around the post 34 and screwed into the internally-threaded lower end of the housing 46; the post 34 is provided with an annular collar 73 fitted against the lower end of the frame 50 which securely holds the extension 34 in position. Leads 74 and 75 extend upwardly from the extension 34 for connection to the moving element of the galvanometer. When desired this assembly may be made fluid tight so that the suspension may be immersed in oil.

As shown in Fig. 9, the moving element of the galvanometer comprises a coil 63 and upper and lower filaments 80 and 81, whichalso constitute the electrical leads for the coil 63. The electrical circuit for the moving element includes the conductor 77 which extends upwardly to the top end of the filament 80 on the pinSS, thence downwardly through the coil 63 and the filament 81 to the conductor 78. The post 34 is an insulator and the contacts 35 and 36 are deposited as annular brush rings on an outer surface of the insulator, the connections being made internally; "this post or connector is of a type available on the market.

During the assembly of the galvanometer element, the

moving element is first assembled within theframe, as indicated in Fig. 9, and is then inserted through the opening at the bottom of the housing 46. The pole pieces 66 and 67 are then inserted in their respective openings 64 and 65 in which they fit closely and the assembly is pushed forward into the housing 46 which thereafter retains the pole pieces firmly in their positions. The frame 50 is then pressed into position until a closure plug 82 at the upper end thereof comes to rest against the shoulder 48. The threaded plug 72 is then inserted in the bottom of the housing 46 to complete the assembly. It will thus be apparent that all parts of the galvanometer assembly are readily accessible for servicing or replacement and that it is not necessary to employ soldering or brazing to secure the magnetic pole pieces in their required positions adjacent the moving coil portion of the suspension. Furthermore, the vgalvanometer element may readily be removed from the cradle in the magnet assembly and it is unnecessary to break any soldered or other fixed connections; the brush and contact assembly at the bottom of the cradle which engages the contacts .35 and 36 of the galvanometer element is automatically made and broken on insertion and removal of the galvanometer housing.

While the invention has been described in connection with the detailed structural features of the preferred embodiment, various modifications and other applications will occur to those skilled in the art. Therefore, it is not desired that the invention be .limited .to the details of construction illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope ofthe invention.

I claim:

I 1. A galvanometer comprising .an elongated frame member of non-magnetic materialh'aving a central axial passage, a galvanometer element suspended in said passage, said frame having a pair of openings therein on opposite sides of said passage, a pair of removable magnetic pole pieces positioned in said openings and spaced from one another on opposite sides of said element, an elongated housing of non-magnetic material fitting closely over said frame in engagement with said pole pieces for enclosing said element and for locking said pole pieces in position, a supporting cradle for receiving said housing, magnetic pole pieces on said cradle positioned to lie adjacent the respective ones of said first mentioned pole pieces when said housing is in position on said cradle, means including a spring pressed detent on said cradle for latching said housing in position therein, a lug on said housing near said cradle, and a lever for exerting force between said cradle and said lug for releasing said housing from said detent.

2. A .galvanometer comprising an elongated frame member of non-magnetic material having a central axial passage, a galvanometer element suspended in said passage, said frame having a pair of openings therein on opposite sides of said passage, a pair of removable magnetic pole pieces positioned in said openings and spaced from one another on opposite sides of said element, an elongated housing of non-magnetic material fitting closely over said frame in engagement with said pole pieces for enclosing said element and for locking said pole pieces in position, a supporting cradle for receiving said housing, magnetic pole pieces on said cradle positioned to lie adjacent the respective ones of said first mentioned pole pieces when said housing is in position on said cradle, means for latching said housing in position in said cradle, a lug on said housing near said cradle, a lever of nonmagnetic material pivotally mounted adjacent said cradle and having a portion positioned to engage said lug for releasing said housing from said latching means, and means including a magnetic body on said lever for biasing said lever toward its operative position.

3. A galvanometer comprising an elongated frame member of non-magnetic material having a central axial passage, a galvanometer element suspended in said passage, said frame having a pair of openings therein on opposite sides of said passage, a pair of removable magnetic pole pieces positioned in said openings and spaced from one another on opposite sides of said element, an elongated housing of non-magnetic material fitting closely over said frame in engagement with said pole pieces for enclosing said element and for locking said pole pieces in position, a supporting cradle for receiving said housing, magnetic pole pieces on said cradle positioned to lie adjacent the respective ones of said first mentioned pole pieces when said housing is in position on said cradle, means including a spring pressed detent on said cradle for latching said housing in position therein, a lug on said housing near said cradle, a lever for exerting force between said cradle and said lug for releasing said housing from said detent, and first electrical contacts connected with said element and mounted on said galvanometer and second electrical contacts on said cradle positioned to be in engagement with said first contacts when said housing is latched in said cradle and to be broken upon release of said housing from said detent.

References Cited in the file of this patent UNITED STATES PATENTS 2,268,526 Palmer Dec. 30, 1941 2,571,776 Stafi Oct. 16, 1951 2,698,417 Hathaway Dec. 28, 1954 

